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| United States Patent |
6,037,864
|
|
Sem
, et al.
|
March 14, 2000
|
Method for continuously determining the oil change interval for an
internal combustion engine
Abstract
A method for determining the oil change interval for an internal combustion
engine for driving a refrigerant compressor. The method includes the steps
of sensing if the engine is being operated at high speed; incrementing the
high speed counter during hours of high speed operation; sensing if the
engine has been stopped; incrementing the counter for number of stops
during the oil change interval; calculating the new oil change interval
based on the current values in the high speed counter and the number of
stops counter; and comparing the calculated new oil interval with the
number of hours of service, and if the number of hours of service exceeds
the new oil change interval, displaying a message indicating an oil change
is needed.
| Inventors:
|
Sem; Thomas R. (Minneapolis, MN);
Hanson; Jay Lowell (Bloomington, MN)
|
| Assignee:
|
Thermo King Corporation (Minneapolis, MN)
|
| Appl. No.:
|
257084 |
| Filed:
|
February 24, 1999 |
| Current U.S. Class: |
340/457.4; 340/679 |
| Intern'l Class: |
B60Q 001/00 |
| Field of Search: |
340/457.4,457,679
|
References Cited
U.S. Patent Documents
| 4506337 | Mar., 1985 | Yasuhara.
| |
| 4533900 | Aug., 1985 | Mulberger et al.
| |
| 4706193 | Nov., 1987 | Imajo et al.
| |
| 4742476 | May., 1988 | Schwartz et al.
| |
| 4796204 | Jan., 1989 | Inoue.
| |
| 4847768 | Jul., 1989 | Schwartz et al.
| |
| 4862393 | Aug., 1989 | Reid et al.
| |
| 4970492 | Nov., 1990 | King.
| |
| 5060156 | Oct., 1991 | Vajgart et al.
| |
| 5382942 | Jan., 1995 | Raffa et al.
| |
| 5530647 | Jun., 1996 | Sem et al.
| |
| 5559494 | Sep., 1996 | Thompson.
| |
| 5592395 | Jan., 1997 | Braun et al.
| |
| 5633796 | May., 1997 | Cullen et al.
| |
| 5642284 | Jun., 1997 | Parupalli et al.
| |
| 5750887 | May., 1998 | Schricker.
| |
Primary Examiner: Hofsass; Jeffery A.
Assistant Examiner: Previl; Daniel
Attorney, Agent or Firm: Gnibus; Michael M.
Claims
Having described the invention, what we claim as our invention is:
1. A method for determining the oil change interval for an internal
combustion engine where the internal combustion engine includes means for
sensing the engine operating speed, means for sensing if the engine has
been started or stopped, and engine processor means for calculating new
oil change intervals; the method comprising the steps of:
a) sensing if the engine is being operated at high speed;
b) sensing if the engine has been stopped or started;
c) calculating a new oil change interval based on the values of time of
operation at high speed and the number of engine stops; and
d) determining if an oil change is required by comparing the calculated new
oil interval with the number of hours of engine service since the last oil
change.
2. The method as claimed in claim 1 wherein the processor includes a high
speed counter, the method comprising the additional step of incrementing
the high speed counter for time of engine operation at high speed.
3. The method as claimed in claim 1 wherein the processor includes an
engine start/stop counter, the method comprising the additional step of
incrementing the engine start/stop counter for counting the number of
engine starts and stops.
4. The method as claimed in claim 1 wherein the processor includes means
for displaying a message, the method comprising the additional step of
displaying a controller message indicating an oil change is needed if the
value of hours of engine service exceeds the new oil change interval.
5. The method as claimed in claim 1 wherein the new oil change interval is
determined by an algorithm based on operating conditions comprised of
running the engine at high speed 20% of the operating time and at low
speed 80% of the operating time.
6. The method as claimed in claim 5 wherein the algorithm for calculating
the new oil change interval is equal to the sum of: a first factor equal
to (total time of engine operation at high speed subtracted from 3600) and
a second factor equal to the product of (the value of the number of starts
and stops subtracted from 3000) multiplied by 0.20.
7. The method as claimed in claim 5 wherein the algorithm for calculating
the new oil change interval is equal to the sum of: a first factor equal
to (total time of engine operation at high speed subtracted from 1800) and
a second factor equal to the product of (the value of the number of starts
and stops subtracted from 1500) multiplied by 0.20.
8. The method as claimed in claim 1 wherein the processor includes means
for counting hours of engine service between oil changes, the method
comprising the additional step of reading the hours of engine service
between oil changes.
9. A method for determining the oil change interval for an internal
combustion engine for driving a refrigerant compressor which supplies
refrigerant to a temperature control system, where the internal combustion
engine includes means for sensing the engine operating speed, means for
sensing if the engine has been started or stopped, and engine processor
means for calculating new oil change intervals; the method comprising the
steps of:
a) sensing if the engine is being operated at high speed;
b) sensing if the engine has been stopped or started;
c) calculating a new oil change interval based on the values of time of
operation at high speed and the number of engine stops; and
d) determining if an oil change is required by comparing the calculated new
oil interval with the number of hours of engine service since the last oil
change.
Description
BACKGROUND OF THE INVENTION
The invention relates to a method for continuously determining the oil
change interval for an internal combustion engine, and more specifically
the invention relates to a method for continuously determining the oil
change interval for an internal combustion engine where the oil change
interval is based primarily on the number of engine starts and stops and
time spent operating the engine at high speed.
A conventional mobile temperature control system includes a prime mover
which may be an internal combustion engine such as a diesel engine. Such
prime movers commonly drive refrigerant compressors which in turn pump
refrigerant through the temperature control system to achieve and maintain
the required temperature in a conditioned space.
It is well known that the oil lubricating the component parts of the
internal combustion engines has a finite useful life and as a result, the
oil must be changed before it becomes unsuitable to lubricate the engine
components. If the oil is not changed before it becomes unsuitable for
lubrication of the engine's component parts, the engine's useful life
could be negatively affected. Conversely, changing the oil too soon before
it becomes unsuitable for lubrication would result in a waste of oil.
Therefore, methods have been developed to more precisely determine when
lubricating oil needs to be changed.
The oil change interval is often affected by engine rotational speed which
causes oil oxidation. It can be difficult to precisely determine the
required oil change interval based solely on engine speed because the
engine speed is typically variable during operation of the temperature
control system and moreover, it is difficult to predict the engine speed
because the engine speed varies according to a plurality of factors
including: the characteristics of the load in the cargo space being
conditioned by the temperature control system, the set point temperature
of the conditioned space, the ambient temperature, and the frequency of
the openings of the conditioned space access door during cargo transfers.
Prior art inventions have addressed determining the required oil change
interval based on engine speed. For example, U.S. Pat. No. 5,530,647
issued assigned to Thermo King Corporation discloses a method for
dynamically determining the oil change interval for an internal combustion
engine by accumulating operating time for an internal combustion engine
operating at high and low engine speeds; and after summing the accumulated
operating information, determining if the engine has reached a
predetermined operating level. If the engine has reached the predetermined
operating level, the operator is informed that the oil needs to be
changed.
Other prior art inventions relate to systems and methods for determining
the oil change interval based on the level of undissolved particulate
matter in the oil. U.S. Pat. No. 4,506,337 issued assigned to Nissan Motor
Company; and U.S. Pat. No. 5,750,887 issued assigned to Caterpillar
Incorporated disclose methods for determining when engine oil needs to be
changed by determining if the amount of undisolvable soot or particulate
matter in the oil exceeds a predetermined level.
Known prior art temperature control systems and methods do not calculate
the oil change interval based on the number of engine starts and stops.
Engine starts and stops increase the oil carbon content through "carbon
loading". During starting and stopping of the engine increased amounts of
carbon are introduced in the engine oil. Carbon-containing blow by
combustion gas that leaks past the rings to the engine block makes contact
with oil, and mixes with the oil, and in this way, carbon loads the oil.
Increased carbon content in the oil shortens the requisite oil change
interval. It would be beneficial to calculate the oil change interval
based on starting and stopping the engine to consider the effects of
carbon loading on the oil change interval.
The foregoing illustrates limitations known to exist in present devices and
methods. Thus, it is apparent that it would be advantageous to provide an
alternative method directed to overcoming one or more of the limitations
set forth above. Accordingly, a suitable alternative method is provided
including features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
In one aspect of the present invention, this is accomplished by providing a
method for determining the oil change interval for an internal combustion
engine based primarily on the number of times the engine is started or
stopped. The method includes the steps of sensing if the engine is being
operated at high speed; incrementing the high speed counter during hours
of high speed operation; sensing if the engine has been started or
stopped; incrementing the counter for the number of engine starts and
stops during the oil change interval; calculating the new oil change
interval based on the current values in the high speed counter and the
start/stop counter; and comparing the calculated new oil interval with the
number of hours of service, and if the number of hours of service exceeds
the new oil change interval, displaying a message indicating an oil change
is needed.
The foregoing and other aspects will become apparent from the following
detailed description of the invention when considered in conjunction with
the accompanying drawing figures.
DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 is a part schematic representation part box diagram of a transport
refrigeration system having an internal combustion engine which has
variable oil change intervals determined in accordance with the method of
the present invention;
FIGS. 2a and 2b taken together represent a flow diagram of a program for
determining the oil change interval for an internal combustion engine
based on operating time at high engine speed and the number of engine
starts or stops;
FIG. 3 is a flow diagram representing the program for sensing that an oil
change has been made and initializing controller counters and clearing the
alarm display.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawings wherein like parts are referred to by the same
number throughout the several views, and particularly FIG. 1, there is
shown a partially block, partially schematic diagram of mobile temperature
control unit, generally identified at 10. The mobile temperature control
unit maintains the temperature of the air or other ambient fluid in a
closed conditioned space 11 which may be a truck, trailer, container or
the like.
Mobile temperature control unit 10 includes components common to such well
known temperature control units. Unit 10 includes refrigerant compressor
12 driven by an internal combustion engine 14, which may be a diesel
engine for example. The engine drives the refrigerant compressor through
drive coupling 16 in a conventional manner, well known to one skilled in
the art at a low speed of 1450 RPM, and at a high speed of 2200 RPM. The
refrigerant compressor may be a reciprocating or scroll type compressor.
An oil level switch 44 is arranged to be responsive to a level of
lubricating oil 41 disposed in oil sump or crankcase 40 of engine 12. Oil
level switch 44 is electrically connected to controller 26 by line 43 that
extends between the controller and an electrical contact of an oil level
switch. The switch contact is open when the oil level 42 is in an
acceptable range. The switch is closed when the oil level is not in the
predetermined acceptable range. Thus oil level switch 44 provides an input
voltage to the controller 26 when the oil level drops below an acceptable
level, such as during an oil change.
A conventional speed sensor 24 senses the operating speed of the engine and
provides the actual engine speed to microprocessor based controller 26. An
hour meter measures the elapsed time of engine operation between oil
changes. The hour meter is made integral with the microprocessor based
controller in a conventional manner and accumulates engine operating time
between oil changes. The sensed elapsed time of engine operation may be
referred to hereinafter as "HIS", an abbreviation for hours in service.
The hour meter is located on the engine in a conventional manner to be
operable to sense engine operation.
Temperature control system 22 is flow connected to the refrigerant
compressor 14 by compressor suction and discharge lines 18 and 20
respectively. The temperature control system collectively represented at
22 includes conventional well known components (not shown) including, but
not limited to a condenser for removing heat from the refrigerant, an
evaporator for removing heat from the air in the conditioned space, an
expansion valve for metering the flow of refrigerant to the evaporator
coil, and refrigerant flow lines flow connecting the refrigerant
compressor, condenser, expansion valve, and evaporator.
Operation of mobile temperature control unit 10 is monitored and controlled
by the microprocessor based controller 26. Controller 26 is a conventional
microprocessor based controller and includes a read-only-memory (ROM) 28
which stores application programs and the like, and a random-access-memory
(RAM) 30 which stores counter values, variables, new oil change intervals
and the like. Programs 100 and 200 illustrated in FIGS. 2a, 2b, and 3 is
stored in ROM 28.
Unit 10 also includes an interactive display 32. The interactive display
includes an alpha numeric readout 34 such as for displaying selected set
point temperature, alarm codes, and the like, push buttons 38 for
interactive communication by authorized personnel with controller 26, and
visual indicators and alarms in the form of indicator lights 36. The
display is electrically connected to the controller in signal receiving
and signal transmitting relation with the controller 26.
Operation of the method of the present invention for determining the oil
change interval will now be described.
FIGS. 2a and 2b taken together represent program 100 for continuously
determining the oil change interval for internal combustion engine 12. The
program 100 is stored in ROM 28 and the program 100 is periodically
entered at step 102 and step 104 determines if engine 12 is running. For
example, in this step, the controller may determine if the engine is
running by determining if an engine fuel solenoid is energized. If the
engine is not running the program exits at return step 105. If the engine
is running, additional program steps are executed. If the engine is not
running, no additional program steps are executed.
When the engine is running, the microprocessor hour meter is updating the
value of hours in service (HIS) in RAM 30.
In step 106 the program determines if the engine is operating at high speed
(2200 RPM). If the engine is operating at high speed, the high speed
counter (HSH) tabulating the hours of engine operation at high speed, is
incremented in step 108. If in step 106 the engine is deemed to be running
at low speed, the program jumps downstream of step 108 to step 110.
In step 110, the routine determines if the controller has started or
stopped the engine since the routine step was last executed. If the engine
was started or stopped the engine start/stop counter (NS) is incremented
for each start or stop.
We have found that on the average, a dual speed transport refrigeration
unit will operate about 20% of the time at high speed and the remaining
time, about 80% at low speed. For diesel engines used to drive refrigerant
compressors, in transport temperature control units, the engine oil should
be changed after 1500 operating hours if the engine runs at the average of
20% high speed and 80% of low speed, 300 hours at high speed and 1200
hours at low speed. The 1500 hour benchmark is for naturally occurring
engine oil.
The formula we have developed for determining the oil change interval for
an engine that uses standard oil based on engine speed and the number of
starts or stops reads as follows:
##EQU1##
Additionally, we have found that for an engine using a mineral or synthetic
oil, the engine may run for longer periods of time between oil changes. In
these instances the maximum running time is 3,000 hours 20% at high speed
and 80% at low speed. The equation for determining oil change interval
operation with a synthetic or mineral oil based on engine speed and
operating time at high speed is as follows:
##EQU2##
For example, for naturally occurring oil, if the engine has been operated
at high speed for 300 hours and the engine has been stopped 20 times the
oil change interval would be:
1800-300+0.20(1500-20)=1796 hours
If the engine is then operated for ten more hours at high speed, and
stopped once more, the new oil change interval would be reduced as follows
:
1800-310+0.20(1500-21)=1785.8 hours
In step 114, the new oil change interval is calculated using the equation
that corresponds to the type of engine lubricant being used. In both
equations the updated value of high speed hours of operation (HSH) and
number of starts and stops (NS) are inserted into the equation to
calculate the new oil change interval. Depending on the changes in engine
operating conditions that occur over time, the oil change interval may
stay substantially constant or may decrease incrementally.
In step 116 the HIS value is obtained from the hour meter and then in step
118 the new oil change interval is compared to the current reading in the
engine hour meter obtained in step 116. If the new oil change interval is
greater than or equal to the number of hours the engine has been in
service since the last oil change, as determined in step 118, an alarm is
displayed on display 32 that an oil change is required. If the hour meter
reading exceeds the new oil change interval, no message is sent to the
unit operator. The alarm may be displayed on alphanumeric screen 34 or
indicators 36 may be illuminated. The alarm light will remain illuminated
and the message will remain on the screen until the oil is changed.
Program 200 in FIG. 3 represents the logic for determining if the engine
oil has been changed and for resetting the counters if the oil has been
changed. After entering the program in step 202, the routine confirms that
the engine is off in step 204 by sensing whether a fuel solenoid is open
or in another conventional manner. Once it is determined that the engine
is not running in step 204, the routine executes step 206 to determine if
the oil has been changed. If after the engine is stopped the engine is
drained from sump 40, the oil level switch is closed thereby providing a
voltage to the controller. After the new oil is added to the crankcase,
the oil level switch will open. This change in voltage to the controller
will cause the controller logic to sense that the engine oil has been
changed.
In steps 208 and 210, after if has been determined that the engine oil was
changed, the controller resets the start/stop and high speed counters NS
and HSH, and the microprocessor engine hour meter. Additionally in step
210 the display alphanumeric screen 34, and/or visual alarm 36 are
returned to their prealarm conditions.
The oil change interval constantly changes during unit operation as a
result of variations in the operating parameters of the internal
combustion engine. For example, extensive high speed operation or frequent
engine starts and stops will decrease the oil change interval. The method
of the present invention determines the new oil change interval based on
high speed operation and the number of engine starts and stops. The
starting and stopping induces carbon loading of the oil and the high speed
affects oil oxidation. Carbon loading and oxidation are two occurrences
that hasten the degradation of the oil. By the present method the oil
change interval may be determined more precisely than with prior art
methods.
While we have illustrated and described a preferred embodiment of our
invention, it is understood that this is capable of modification, and we
therefore do not wish to be limited to the precise details set forth, but
desire to avail ourselves of such changes and alterations as fall within
the purview of the following claims.
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